Solar cell lead making machine

Our universities solar car team is in a mad dash to get their car completed for next month's (July 2008) NASC solar car race. They are panelizing their own cells for the first time and I was asked if I could come up with a way to assemble the leads that for the electrical connections between the individual cells. Another engineer on campus who is an advisor to the team had figured out the design of leads and also took care of making soldering jigs. The leads are three pieces of 0.003" x 0.080 flat ribbon wire spaced 20mm apart in between two pieces of Capton tape.

I had about 1 day to try and get the parts I didn't have on hand before having to leave town. I contacted Warp9 Tech Design and Xylotex and both companies went out of their way to get us the parts on time (a SmoothSteper from Warp9 and a 4 axis stepper driver w/PS pre wired from Xylotex).

It took about a week to figure out how to design/build the machine and a few overnight orders from McMaster-Carr for parts to make it work. The original plan was to have the tape feeder also form a slight 'Z' bend in the lead, but we ran out of time to fabricate the rolling dies. The stepper motor mounts are 1x3x1/8" wall aluminum tubing that I had on hand. I used my Mach III powered bench-top mill to cut the proper openings.

The basic idea is that there is a tractor motor that pulls the twp pieces of (semi-sealed) tape though the machine 20mm at a time. The ribbon feeder then feeds just over 0.4" of ribbon between the two pieces of tape. Finally a tamper cutter cam spins around and semi-seals the tapes together trapping the ribbon which allows a 28mm cutting wheel ( from a Fiskars rotary cutting hand tool ), to cut the ribbon to length. There is about 1MM/2MM of ribbon that protrudes from each side of the 1/4" tape.

While the machine works it is quite touchy to get dialed in. No doubt owing to its rushed design/construction and my lack of experience with making a machine like this. Trying to feed the ribbon wire is like pushing a wet noodle. The aluminum block you see held in place with a C-clamp was a quickly make guide with a hand filed groove and a clear plastic bottom made from the Fiskars cutter package. If I were to do it again I would have the fed roller much closer to the tamper/cutter.

My daughter went in with me today to run some leads and quickly took to running Mach III. I was amazed that she quickly correlated the DRO's with each axis and new which was X, Y and A (Though she wondered why it was A and not Z.)